“Magic Mylar” diffusion material (plus Post Update)

So there I was, working on the next epic sundial-related blog post, when I realized two things: 1) The post needs to be too long to finish before Friday; and 2) The topic probably needs to be covered in a series of posts rather than one long post. Regrettable, because WordPress site statistics shows the sundial-related blog posts are popular with readers of my blog. Anyway, please stay tuned — I hope to finish the next post by Tuesday, 23 May 2023.

In the meantime, I decided to give you a quick update on my never-ending quest for good light diffusers.

“Magic Mylar”

A friend and expert in macro photography kindly shared several sheets of diffusion material with which he is getting great results. The material is made of mylar plastic, matte on both sides.

I should have taken some shots of the same subject with- and without diffused light, but I didn’t have time to do a proper test of the new diffusion material. Qualitatively speaking, I like the look and feel of the test shots in diffused light although I concede there are specular highlights that might require either double- or triple layers of diffusion, as recommended by my friend.

Here are a few shots from a quick studio session. The subject is a highly reflective plastic toy dinosaur. I used a small LED light panel (with added diffusion to supplement the built-in diffuser on the LED) and a Godox TT685C plus a small Altura flash modifier to light the scene. The output from the LED light panel is assumed to be constant, while I slightly increased the distance between the subject and the TT685C from the first to last shot. I estimate the front of the Altura was no more than say 5″ to 7″ from the subject. My assumption is the farther the TT685 was from the subject, the more the LED was the dominant light source.

Closest.

Mid-range.

Farthest.

Where can I get some “Magic Mylar?”

I don’t know whether the results of my test are so impressive that you would like to order some of the “Magic Mylar” STAT. The following image shows the label from a big roll of the mylar.

Comstoc Ink Jet Plotter Media | 3 MIL Double Matte

It’s unclear whether this specific product is discontinued. One source says the art supplier Dick Blick sells sheets of similar material. I will do some research and report my findings, if any. Please comment on this post if you find a source before I do.

Tech Tips

Disclaimer: The following photos show no evidence that I’m actually a fairly good photographer.

Here are two quick-and-dirty shots (taken with my Apple iPad mini 6) that show how I used the mylar to diffuse light from a Sunpak LED 160 light panel. I simply taped an ~8.5″ x 11″ sheet of the mylar to the LED. The first photo shows the LED off; the second shows the LED on.

Sunpak LED 160 light panel. (Off.)

Sunpak LED 160 light panel. (On.)

Looks like I didn’t place the subject at the center of the circle of light. In my defense, the circle of light wasn’t as apparent to me as it is in the photo. Hey, I told you it was a quick-and-dirty test!

More later after further testing.

Post Update

I’m a scientist. No really, I am. I know it’s easier to analyze the results of an experiment that has only one variable. My last experiment included another variable that made it impossible to objectively evaluate the quality of light diffused by adding “Magic Mylar” to a small LED panel.

So I ditched the Godox TT685C external flash unit and photographed the subject using only diffused light from the LED panel.

All photos were taken using my Apple iPad mini 2. Same subject, same “stage.” Notice the subject is closer to the center of the circle of light on the background.

Next I moved the iPad closer to the subject for a better look at the specular highlights, if any.

Finally, here’s the same shot cropped for a closer look at the subject. The white balance is way off, but hey, it’s an iPad camera photo! Otherwise the light has what I would describe as a “warm glow” with fewer glaring specular highlights than the shots from the first test. Maybe now you can see why I am excited by the results of my experimentation with the new mylar diffusion material.

Perhaps you’re wondering, “Why was it necessary to use an external flash unit when you took the first test shots?” I used my Fujifilm X-T5 and 80mm macro lens to take those shots. I wanted to use the same settings that I’ve been using for studio macro focus bracketing. Problem is, the photos were underexposed. Since I didn’t want to change the camera/lens settings, my only option was to add more light. And now you know the rest of the story.

Copyright © 2023 Walter Sanford. All rights reserved.

I love it when a plan comes together!

Do you remember The A-Team, a classic 1980s TV show? One of Colonel John “Hannibal” Smith’s catch phrases was “I love it when a plan comes together!” So do I.

In my last blog post, I wrote the following …

Look closely and you should notice a few places that appear to be artifacts resulting from the focus stacking process. (Look around the borderline between the toy dinosaur and NSTA plastic ruler.) … I must admit this is cause for concern. Source Credit: More testing, AUTO FOCUS BKT, by Walter Sanford.

Could you tell I was more than a little discouraged by the discovery of artifacts in my focus-stacked composite images? I was. So I devised a plan for isolating the cause of the problem and finding a solution.

The plan

First I looked at the source images for the composite images. I didn’t see the same artifacts in any of the JPG files used to create the focus stacks, so I knew that in-camera focus bracketing was working properly in my Fujifilm X-T5.

Next I re-rendered (is that a word?) the source images using Helicon Focus Method A and Method C. My hypothesis, based upon limited experience and knowledge gained by following the “Focus stacking – Helicon Focus” Facebook group, was that rendering Method C would work without creating artifacts.

Turns out I was right. Look closely at the full-size version of the following focus-stacked composite image and you should see the artifacts are gone. And that’s a good thing, because as far as I can tell using the retouching tools in Helicon Focus means “you’re entering a world of pain.” (Source Credit: John Goodman as Walter Sobchak in “The Big Lebowski.”)

Toy dinosaur focus stack: two flashes; 74 frames; rendering Method C.

Buoyed by my success with re-rendering the source images for the composite image of a toy dinosaur, I used Method C to re-render the source images for the composite image of a toy lizard. Same result: Artifact problem solved!

Toy lizard focus stack: one flash; 96 frames; rendering Method C.

So now both composite images are tack-sharp from front-to-back and artifact-free. Yep, I love it when a plan comes together! And looking at the bigger picture, now I know for sure that Fujifilm in-camera AUTO FOCUS BKT works as I hoped and works well. That’s a win-win!

Why do we focus stack?

The composite image of the toy dinosaur, shown above, was created using 74 unedited JPGs straight out of my Fujifilm X-T5 digital camera. All of the photos were shot using an aperture of f/11.

The following slideshow was created using the first, middle, and last photos in the set (frames 01, 37, and 74). The focus point moves from the tip of the head, to somewhere along the body of the toy dino, and to the tip of its tail. In each of the photos, notice how little of the toy and ruler are acceptably in focus — even at a relatively small aperture of f/11. And that, ladies and gentlemen, is why we focus stack!

This slideshow requires JavaScript.

Related Resources

• More testing, AUTO FOCUS BKT – a blog post by Walter Sanford.
• AUTO FOCUS BKT – another blog post by Walter Sanford.
• Helicon Focus online documentation

Copyright © 2023 Walter Sanford. All rights reserved.

More testing, AUTO FOCUS BKT (plus Post Update)

Someone I know is fond of saying “A sample size of one proves nothing.” And that’s true, at least in the case of my recent test of Fujifilm AUTO FOCUS BKT. So I refined my step-by-step instructions slightly and tested the process again. Two times, in fact. And the results are comparable to my first test.

I have learned from experience it’s better to use a rugged toy “model” for testing purposes, rather than one of the fragile odonate exuviae that I like to photograph. It’s a good idea to choose a test subject that’s about the same size as your intended subject. The following toy dinosaur is ~6 cm from head to tail — the same size as the largest specimen in my collection of exuviae.

Two flashes

The following composite image was created using Helicon Focus to focus stack 74 JPG photos taken automatically using my Fujifilm X-T5 set for AUTO FOCUS BKT. The composite image was created using unedited JPGs straight out of the camera.

Toy dinosaur plus NSTA plastic ruler.

As you can see, both the toy dinosaur and NSTA plastic ruler are in focus from front-to-back without any focus banding. Zoom in to look at the full-size composite image — the detail is impressive!

Look closely and you should notice a few places that appear to be artifacts resulting from the focus stacking process. (Look around the borderline between the toy dinosaur and NSTA plastic ruler.)

I used rendering Method B in Helicon Focus. Time permitting, I would like to try Method A and Method C to see whether the artifacts go away. The artifacts are visible in both the “Two flashes” and “One flash” versions of the composite image, and upon further review, also visible in the composite image of the toy lizard featured in my last blog post. I must admit this is cause for concern.

Post Update: I used Helicon Focus rendering Method A and Method C to re-render the composite images: Method A was better than Method B; Method C nailed it! For details, please see my blog post entitled “I love it when a plan comes together!“

One flash

The setup for the “one flash” photo shoot was exactly the same as the “two flashes” version except I used one fewer external flash unit.

The following composite image has higher contrast than the first. Although I like the look, I was curious to see how adding a second flash would affect the final result.

Toy dinosaur plus NSTA plastic ruler.

I’m still undecided about which version I like more, but the order in which they are presented in this post provides a big hint. Which version do you prefer — is less more?

Related Resources

• AUTO FOCUS BKT – a blog post by Walter Sanford. Hey, that’s me!
• Focus Bracketing / Stacking with Fuji XT4 NEW AUTO Feature Stack w/ Photoshop or Helicon Focus, by The Magical Landscape (13:02). AUTO FOCUS BKT works exactly the same way in both the Fujifilm X-T4 and X-T5.

Copyright © 2023 Walter Sanford. All rights reserved.

AUTO FOCUS BKT (plus Post Update)

Let me say at the outset I love my Fujifilm X-T3 digital camera. That being said, I bought the Fujifilm X-T5 almost as soon as it was released.

There are many reasons I decided to buy the Fujifilm X-T5 but the number one reason is the X-T5 features both Auto- and Manual mode focus bracketing while the X-T3 is Manual only.

At some point I’ll revisit MANUAL mode focus bracketing, but this post will focus on AUTO FOCUS BKT. Using AUTO FOCUS BKT, the photographer sets the beginning and ending focus points and the camera selects the step size and number of frames automatically.

Sample output

The following composite image was created using Helicon Focus to focus stack 96 JPG photos taken automatically using my Fujifilm X-T5 set for AUTO FOCUS BKT. The composite image was created using unedited JPGs straight out of the camera.

Toy lizard plus NSTA plastic ruler.

As you can see, both the toy lizard and NSTA plastic ruler are in focus from front-to-back without any focus banding. The process worked surprisingly well and could be a game-changer for creating focus stacks of relatively larger macro subjects.

Step-by-step instructions

The next two images are screenshots from  the online version of the Fujifilm X-T5 Owner’s Manual. From the Table of Contents, click on “Shooting Menus”; from the sub-menu that appears on screen, click on “Shooting Setting (Still Photography).” Click on Drive Setting; navigate to the section entitled “FOCUS BKT SETTING” and look for “AUTO.”

Steps 1-3 …

Image Credit: Fujifilm X-T5 Owner’s Manual.

Steps 4-5 …

Image Credit: Fujifilm X-T5 Owner’s Manual.

Here’s my interpretation of the preceding outtakes from the Fujifilm X-T5 Owner’s Manual. I suggest you follow the set of step-by-step directions that makes more sense to you, although I think they are complementary.

First, a few words of caution about something that can and probably will trip you up the first time you try focus bracketing, using either MANUAL- or AUTO mode. (That’s the voice of experience talking.) You need to make settings in several places including one setting on the camera itself and two MENU settings. All of those settings are highlighted in boldface red text.

1. Set the “Drive dial” [physical dial located under “Sensitivity dial” (ISO)] for BKT.
2. Press MENU/OK. [press left trackpad button] Select Drive Setting (camera icon) > [press right trackpad button]
3. BKT SETTING > [press right trackpad button]
4. BKT SELECT > [press right trackpad button] FOCUS BKT [press OK]
5. [bottom trackpad button] Select FOCUS BKT > [press right trackpad button] AUTO > [press right trackpad button] INTERVAL [set for 10 s [press OK]
6. SET POINT A – Use the “Focus stick (focus lever)” to move the focus point to your desired location. Press the button for back-button focus [AF ON button, by default]. [press OK]
7. SET POINT B – Relocate the focus point. Press the button for back-button focus [AF ON button, by default]. [DO NOT press OK!]
8. BACK, END – Press the DISP/BACK button one time until you see the menu screen where you choose either “MANUAL or AUTO.” [This step seems a little counterintuitive to me, but it works.]
9. Press the “Shutter button.” I recommend a 10 s timer; there is a countdown for the first shot only.

When you are setting focus for Point A and Point B, you can use any method that works for you including simply turning the focus ring on the camera lens. I prefer to use back-button focus. When the camera is set for Manual focus mode (M) the “AF ON” button is used for back-button focus by default. Try it — I think you’ll like it and it just works right out of the box.

I set Point A for the tip of the lizard’s nose and Point B for the tip of its tail.

Tech Tips

X-T5 camera/lens settings: f/11; ISO 200; 1/250 s. White balance set for AUTO WHITE PRIORITY WBW. Single point focus. Number of Focus Points set for 425. “Focus mode selector” set for “M” (Manual focus).

Off-camera lighting:

• Godox XProF flash trigger
• Godox MF12: Modeling light = 10/10; flash power ratio = 1/8.

Bear in mind I didn’t really worry about lighting the subjects properly. I chose to use one external flash unit that I knew from experience would work reliably at 1/8 power. I’m pleased to report there weren’t any “dropped frames” due to flash failure.

Interval: 5 s ← Note: The built-in camera timer doesn’t work when using focus bracketing (except for the first photo) so I recommend you increase the  Interval to 10 s in order to give your camera time to settle between shots and plenty of time for your external flash units to power-cycle.

Subject: Toy lizard plus NSTA ruler = 96 frames (selected by camera automatically).

Background/”stage”: White reference card from a Vello White Balance Card Set (Small), and NSTA plastic ruler.

What are the take-aways?

My goal was to test the Fujifilm in-camera photo bracketing process using “AUTO” mode.  Zoom in to look at the full-size image — the detail is impressive! I’d say the test was a complete success. Well, mostly successful. For details, see “More testing…” under Related Resources.

Related Resources

• Focus Bracketing / Stacking with Fuji XT4 NEW AUTO Feature Stack w/ Photoshop or Helicon Focus, by The Magical Landscape (13:02). AUTO FOCUS BKT works exactly the same way in both the Fujifilm X-T4 and X-T5.
• More testing, AUTO FOCUS BKT – another blog post by Walter Sanford.
• I love it when a plan comes together! – the final blog post in what turned out to be a three-part series.

Post Update

Chris Lee, also known as “pal2tech,” released a related YouTube video after I published my blog post: “Why I LOVE This Fujifim Lens! (30mm Macro),” by pal2tech (11:26). Although the main theme of the video is a detailed review of the macro lens, there is an embedded segment related to how to use AUTO FOCUS BKT and Helicon Focus beginning at the 05:05 minute mark and ending at ~07:47: “How To Focus Stack With Fujifilm Macro Lens.” Well done, Chris!

It’s worth noting I disagree with Chris’s recommendation of the Fujifilm XF30mm F2.8 R LM WR Macro lens. Regular readers of my blog know I’m all about macro photography and don’t need much of an excuse to buy more gear. I considered this lens carefully when it was announced and rejected it as a bad fit for my needs.

Chris has valid reasons for liking the lens and I have valid reasons for disliking it — we just disagree, that’s all. For example, Chris raves about how close you can get to the subject with this lens. Sounds good, but the reality is a small working distance makes it much more challenging to light the subject properly. And Chris readily concedes the lens isn’t perfect, optically speaking.

Bottom line: I strongly recommend the tutorial segment of Chris’s video while cautioning my readers to carefully consider whether this lens would be a good fit for your macro photography needs.

Copyright © 2023 Walter Sanford. All rights reserved.

Making progress (on a steep learning curve)

OK, let me say right at the outset that using a manual focus rail like my new-ish NiSi NM-200 to create a 328-photo focus stack is insane! So I regrouped, made a new plan, and conducted some tests.

I discovered, albeit too late, that I needed to shoot a lot of  photos for my last focus stack because I chose to use an aperture of f/8 and the “safe step size” for f/8 (at 1x magnification) is 40 µm (micrometers, or microns) — a relatively small step size.

In contrast, at 1x magnification the safe step size for f/11 is 800 µm — during limited testing that seems to be the sweet spot for creating focus stacks that look fairly good using fewer photos.

Canon EOD 5D Mark II DSLR camera plus Canon EF 100mm macro lens (1x, f/11)

The following composite image was created from 20 photos.

The background is the non-reflective side of a piece of black plastic. It’s textured surface appears to be a bad fit for macro photography — notice lots of little white specks on the background. Not good.

f/11 | 1/200 s | ISO 100 | Manual WB (Flash)

But wait, there’s one more thing. Did you notice the copper penny hiding underneath the quarter? Well, it was supposed to be hiding. I borrowed the idea from another photographer whose name I can’t remember. The point is to create some visual relief for the coin in the photo. The plan might have turned out OK if I’d noticed the misalignment of the penny before I did the focus bracketing.

Fujifilm X-T5 mirrorless digital camera plus Fujinon 80mm macro lens (1x, f/11)

The following composite image was created from 26 photos.

For the background, I used the white reference card from a Vello White Balance Card Set (Small). I set the white balance for AUTO WHITE PRIORITY WBW — a new setting (at least new to me) that’s supposed to result in whiter whites.

f/11 | 1/250 s | ISO 125 | WBW

The subject is in focus from back-to-front, and I like the white background. I think this is the best composite image I’ve created so far, but as always, you be the judge.

Fujifilm X-T5 mirrorless digital camera plus Fujinon 80mm macro lens (1x, f/11)

The following composite image was created from 21 photos.

For the background, I used the black reference card from a Vello White Balance Card Set (Small). I think it looks better than the textured black plastic background in the first photo, although I think the white background looks best.

f/11 | 1/250 s | ISO 125 | WBW

Pixel-peepers will notice the far end of the nickel isn’t as sharp as the rest of the coin. That’s because a man-caused disaster forced me to leave out the first two photos in the set. I hope the man responsible for this sloppy work will be held accountable for his actions!

Tech Tips

I think it’s worth noting that all three composite images were created using unedited JPGs straight out of the camera. All of the composite images could have been improved by making a few edits to the RAW files such as adjusting exposure, increasing contrast, and adding a little sharpening, to name a few.

In these test cases, I was looking for focus banding caused by using a step size that’s too big and glitches caused by Helicon Focus, the focus stacking software I used. As far as I can see, no problems.

My NiSi NM-200 is mounted on a Manfrotto 405 3-Way, Geared Pan-and-Tilt Head. The camera line of sight was inclined at a 45° angle relative to the staging surface. That’s less important in this case and more important for an upcoming review of the NiSi NM-200 focus rail.

Both cameras were set for manual exposure. Both lenses were set for manual focus; the combination of manual focus and back-button [auto]focus gives me the best of both worlds.

I use single point focus nearly all the time. I moved the focus point to the farthest point of each subject, then used back-button focus to autofocus on the subject and shoot a photo. Without changing focus from the first photo, I used the focus rail to move across the subject from back-to-front in 800 µm increments (eight numbered increments on the NiSi larger adjustment knob), taking a photo at each step.

More light is required for proper exposure at f/11 than f/8. I used one Sunpak LED-160, one Godox TT685C external flash unit (plus Altura flash modifier), and one Godox MF-12 external flash to light the first subject (Virginia quarter). Two Sunpak-160s and two Godox TT685C external flash units (using Altura and Lastolite flash modifiers) were used to light the last two subjects (quarter and nickel coins).

Related Resources

• Zerene Stacker DOF Calculator
• Fujifilm Colors: Auto White vs Auto Ambience, by pal2tech (12:47)
• Helicon Focus – Quick Start on Mac OS, by HeliconSoft (2:20)

Copyright © 2023 Walter Sanford. All rights reserved.

Comedy of errors

My first big focus stack turned out to be a comedy of errors. Lots of little things, all of them avoidable, but the one that broke the stack was when the camera battery died approximately two-thirds of the way through the project.

My new Fujifilm X-T5 has a much larger battery than my Fujifilm X-T3 so I never imagined it wouldn’t last long enough to create the stack.

I might have been able to salvage the stack by changing the battery without removing the camera from the focus rail, but the Manfrotto quick release plate partially blocked the battery door. Doh!

l use Arca Swiss L-brackets for all of my cameras. Good L-brackets are designed so the bracket doesn’t block any camera doors or ports. But I don’t have one for the X-T5 because it’s new enough that the selection of compatible L-brackets is poor.

I have two ways to provide continuous power for the X-T5 but I couldn’t use them because the battery door was partially blocked. Double doh!

Making lemonade from lemons

Long story short I used Helicon Focus to stack all the photos up until the power failure and the results look fairly good, as shown below. Oh what might have been. Triple doh!

ISO 400 | 80mm | 0 ev | f/8 | 1/250 s

The preceding composite image was created from 192 of 328 photos. I used a safe step size of 50 µm (microns) between photos. Each JPG photo is ~13 MB, 7728 × 5152 pixels.

The coin is acceptably in focus from the top of the coin to a point about two-thirds of the way toward the bottom. Zoom in on the horse’s head and you should notice sharp focus is lost beginning below its eye.

The amount of detail in the composite image is astounding, as shown in the close-up of the upper-right quadrant.

Close-up, upper-right quadrant.

Related Resource: Post update on 11 April 2023.

Copyright © 2023 Walter Sanford. All rights reserved.

Focus bracketing and focus peaking

Focus peaking can be used to visualize areas of a photograph that are acceptably in focus. This can be especially helpful when creating focus stacked composite images.

I recorded two videos that show simulated focus bracketing using my NiSi NM-200 manual focus rail. Notice how the focus peaking band moved across the subject from back-to-front as the carriage moved along the lead screw of the focus rail. The videos aren’t rock steady because I was turning the larger adjustment knob as I was recording the HDMI output from two of my Fujifilm X Series digital cameras.

The subject in both videos is a quarter, that is, a 25-cent coin in U.S. currency. President Theodore Roosevelt is shown on one side of the coin.

The diameter of a quarter is 24.257 mm (0.955 inches). The APS-C sensor used in Fujifilm X Series digital cameras is 23.5 mm x 15.7 mm. A good indicator of the magnification is how much of the quarter is visible in the photo frame.

Fujiffilm X-T3 camera plus Laowa 25mm Ultra Macro lens

The following YouTube video shows a simulation of focus bracketing using a Fujiffilm X-T3 digital camera plus Laowa 25mm Ultra Macro lens. Focus peaking (shown in red) helps to highlight areas of the image that are acceptably in focus.

Video of Roosevelt quarter at 2.5x magnification using an aperture of f/4.

Fujiffilm X-T5 camera plus Fujinon 80mm macro lens

The next YouTube video shows a simulation of focus bracketing using a Fujiffilm X-T5 digital camera plus Fujinon 80mm macro lens. Focus peaking (shown in red) helps to highlight areas of the image that are acceptably in focus, same as in the preceding video. Although it’s not an apples-to-apples comparison, I set the lens aperture to f/4, like the X-T3/Laowa macro rig.

Video of Roosevelt quarter at 1x magnification using an aperture of f/4.

Safe step size and focus banding

After watching the preceding videos, I think it should be clear why macro photographers use focus bracketing to create focus stacked composite images that show more depth of field than is possible from a single photo.

Focus peaking helps to highlight areas of an image that are acceptably in focus. Focus banding occurs when there isn’t enough overlap between the areas that are in focus from one image to the next. This is why it’s critically important to calculate the safe step size BEFORE you begin a focus stacking project.

Tech Tips

The following YouTube video shows how to set my Fujifilm X Series cameras for “clean HDMI” video output. Sometimes it’s helpful to turn “ON” the info display, for example, when creating “how to” videos like this one. You can see my camera settings at the beginning and end of the video.

Video of Menu settings for “clean HDMI.”

A micro-HDMI cable was used to connect my cameras to a MacBook Air (13″, M1, 2020) laptop computer via an inexpensive HDMI Video Capture adapter (HDMI to USB). I used Apple QuickTime Player (free) to record the HDMI video output from my cameras.

Open Apple QuickTime Player. File / New Movie Recording. Click the down arrow disclosure button located to the right of the red Record button and make the following settings.

• Camera = USB Video [= HDMI adapter]
• Microphone = MacBook Air Microphone [for narration, voice over]
• Quality = Maximum [1920 x 1080p, 25 fps]

Movies are recorded as .mov files.

Related Resources

• BEST Fujifilm Manual Focus Setting! by pal2tech (6:01) – FOCUS PEAK HIGHLIGHT plus Fujifilm film simulations (“Acros” Black and White)
• Understanding Fujifilm Video Recording, by pal2tech (5:11)
• Fujifilm X-T3: Focus Peak Highlight – A blog post by Walter Sanford related to, well, focus peaking.
• What is it? – A blog post by Walter Sanford related to the HDMI Video Capture adapter used to create the videos featured in this post.

Copyright © 2023 Walter Sanford. All rights reserved.

 

Please stay tuned …

I’m working on a blog post that isn’t ready for publication. It should be finished sometime within the next day-or-so, so as the title says, please stay tuned.

Walter

How to measure magnification, revisited

The magnification of any macro photography rig can be determined by using the rig to photograph a metric ruler such as the one shown below.

Plastic 15 cm (6″) ruler from the Natl. Science Teachers Assn. (NSTA).

The following photograph was taken using a Laowa 25mm Ultra Macro lens mounted on my Fujifilm X-T3 digital camera. The lens was set for 2.5x magnification and an aperture of f/4, the “sweet spot” for this lens. Notice that only a small part of the ruler is shown in this “full frame” (uncropped) macro photo.

Segment of an NSTA metric ruler.

The formula for magnification is as follows.

length of camera sensor, in mm / #mm visible in photo frame

Both measurements must be expressed in the same units in order for the units to cancel during division.

The APS-C digital sensor featured in the Fujifilm X-T3 is 23.5 mm long. The annotated image shows ~9.0 mm of the small plastic ruler is visible in the photo frame.

23.5 mm / ~9.0 mm = ~2.6x

Is the actual magnification of the Laowa 25mm Ultra Macro lens slightly greater than 2.5x? I don’t know, but my calculation confirms the minimum magnification setting for the lens is in the neighborhood of 2.5x and that’s good enough for government work.

Photo Credit: Venus Optics.

What are the take-aways?

As a result of photographing the ruler, subject selection should be easier. Now I know ~9 mm is the size limit for subjects to fit entirely within the photo frame when the lens is set for 2.5x magnification. That’s actionable intel.

Related Resources

• How to Calculate Your Camera’s Magnification in Macro Photography, by Stewart Wood (12:02).
• How to measure magnification – a blog post by Walter Sanford that features instructions for using either Adobe Photoshop or Photopea to make measurements of photos.

Copyright © 2023 Walter Sanford. All rights reserved.

Post update: What is it?

The mystery object shown in my last blog post is a macro composite image of the right eye of Benjamin Franklin, as he appears on a $100 bill. The $100 bill is the largest denomination Federal Reserve note currently issued for public circulation.

Image Credit: Wikimedia Commons.

Tech Tips

2.5x magification | aperture f/4 | shutter speed 1/250 s | ISO 160

The preceding image is a focus stacked composite of 77 JPG photos taken with my Fujifilm X-T3 digital camera plus a Laowa 25mm Ultra Macro lens. The lens was set for 2.5x magnification and an aperture of f/4, the “sweet spot” for this lens.

The camera was mounted on my NiSi NM-200 manual focus rail. A safe step size of 50 microns was used in order to avoid focus banding, as determined by using Zerene Stacker DOF Calculator.

For better composition of the final composite image, I created the stack by focusing past the farthest focus point and moving the rail backward to slightly beyond the closest focus point. (Remember, the subject looks bigger at the farthest focus point than the closest. This almost certainly means it will be necessary to crop the final image if you shoot front-to-back. Going back-to-front helps to avoid this problem.)

The carriage of the focus rail traveled a total distance of 3.85 mm.

77 steps/1 x 50 microns/step = 3,850 microns

3,850 microns/1 x 1 mm/1,000 microns = 3.85 mm

77 steps is probably more than necessary but I wanted to be sure the entire image is acceptably in focus.

Helicon Focus was used to create the focus stack. The final rendering is saved as a TIF file, by default. I converted the TIF to JPG for posting in my photoblog. The final output, shown above, is unedited otherwise.

Sidebar

A micrometer (also known as a micron) equals 0.001 of a millimeter, or 1/1,000 of a millimeter. In other words, there are 1,000 micrometers in one millimeter. The symbol for micrometer is µm.

Related Resources

• Zerene Stacker DOF Calculator
• Helicon Focus – Quick Start on Mac OS, by HeliconSoft (2:20)

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